Oxazolidinones are a class of compounds containing 2-oxazolidone in the structure. Oxazolidinones are mainly used as antimicrobials. The antibacterial effect of oxazolidinones is by working as protein synthesis inhibitors, targeting an early step involving the binding of N-formylmethionyl-t-RNA to the ribosome.
Linezolid is the first synthetic oxazolidinone class of antibacterial agent and is chemically known as (S)-N-[[3-[3-fluoro-4-(4-morpholinyl)phenyl]-2-oxo-oxazolidin-5-yl]methyl]-acetamide and can be represented by the structure of general Formula I.

Linezolid is indicated in the treatment of infections caused by susceptible strains of the designated microorganisms such as Vancomycin-Resistant Enterococcus faecium, Nosocomial pneumonia, complicated skin and skin structure infection, uncomplicated skin and skin structure infections, community-acquired pneumonia and is commercially sold under the brand name Zyvox®.
Linezolid is first disclosed in U.S. Pat. No. 5,688,792. This patent also disclosed a process for the preparation of Linezolid, which is as depicted in scheme-I given below:

PCT Publication No. WO 1999/24393 A1 discloses a process for the preparation of oxazolidinone derivatives which is depicted in the scheme-II given below:
where Roxa is phenyl substituted with one fluoro and one substituted amino group, wherein the substituted amino groups include 4-(benzyloxycarbonyl)-1-piperazinyl, 4-morpholinyl and 4-hydroxyacetylpiperazinyl.    X1 is C1-C20 alkyl;    X2 is Cl, Br    RN is C1-C5 alkyl    # indicates that the atoms marked with (#) are bonded to each other resulting in the formation of ring    and RING is

However, WO '393 does not disclose any specific examples or suitable conditions for the preparation of Linezolid and moreover, the use of lithium on commercial scale is not feasible.
PCT publication No. WO 2005/099353 A2 discloses a process for the preparation of Linezolid. The process is depicted in scheme-III given below:

PCT publication No. WO 2006/008754 A1 discloses a process for the preparation of Linezolid. The process is depicted in scheme-IV given below:

Condensation of 3-fluoro-4-morpholinyl aniline with epichlorohydrin may result in the formation of N,N-dialkylated compound as an impurity, which may be difficult to remove and effects the overall yield. Further, the process requires the use expensive reagents like carbonyl diimidazole during the carbonylation, which is hygroscopic and difficult in handling.
Thus there is a need in the art for an improved process for the preparation of Oxazolidinone derivatives, which employs less expensive, easily available and environment friendly reagents.